1. Field of the Invention
The present invention relates generally to a switchable ratchet freewheel for multiple-gear hubs for bicycles, including at least one pawl at the end face of a drive. The pawl is pivoted on a bolt that runs parallel to the hub axis. The switchable ratchet freewheel also includes a switch ring with pawl pockets for accommodating a catch nose of the pawl and a switch bush that is movable to and fro in the direction of engagement, which switch bush can have a make-and-break contact with a switch nose that is formed on the pawl.
2. Background Information
With German Laid Open Patent Application No. 29 37 126 a control mechanism for a catch pawl with a switch hub for a bicycle is described. A pawl control link that can be slid against a catch pawl in the axial direction is shown, whereby the catch pawl shows an incline. The pawl control link is, by means of an actuating link, axially movable but placed so that it is safe against rotation. A slanted incline on the pawl control link, matching the incline of the pawl, is equipped with pockets which allow the actuating link to move the pawl control link, at certain sections, a little further in the direction of the catch pawl. The transitions of the pockets in the pawl control link shall cause the transition of the catch pawl from the catch position to the rest position to be faster and speedier. A modulating force can be generated for the catch pawl, corresponding to the incline of the pocket vis-a-vis the incline of the catch pawl. However, should the catch force be even higher with an engaged catch pawl, the pawl control link and with it the actuating link are rejected and moved back opposite the control direction. In order to avoid such motion, the present invention has created the possibility that a switch bush, corresponding to the pawl control link, can no longer move axially against a pawl but rather under the pawl with a timing edge. Such an arrangement ensures that the pawl, by means of recesses and timing edges, can also be lifted when a drive load exists that is considerably higher than the control force of the switch bush.
Furthermore, with German Patent No. 44 15 266.3 A1, which corresponds to U.S. Pat. No. 5,556,354, a switching device for change-speed gears in multiple-gear hubs for bicycles is disclosed which includes several coaxially lined-up switching levels. Switch cam rods that are placed on the surface of the hub axis, coaxially to same, become swivelable around their axis by means of a cam control. Pawl couplings that are placed on a larger diameter in the change-speed gear of the hub can simultaneously, and in a coordinated manner, be controlled by the afore-mentioned cam control of the sun wheel. Such a switch clutch is realized with a switch sheath that is movable in the axial direction. The switch sheath shows an incline that can be slid under the pawls of the pawl coupling in order to lift them. The switch sheath shows an incline which moves a bolted pawl outward by lifting the part of the pawl that points radially inward, and thus disengages the pawl bond with a switch ring that is placed outside. A switch sheath with recesses, which slides under the pawl over the entire pawl width, is not suggested.